Kary Banks Mullis, Ph.D., a 1993 Nobel Laureate in chemistry for groundbreaking work involving DNA, will speak on "Paradigms: Plausible Fables in Science" at 1 p.m. Friday, May 1, in Science 142. Mullis received the Nobel Prize for his invention of the polymerase chain reaction (PCR). The process has been hailed as one of the monumental scientific techniques of the 20th century. A method of amplifying DNA, PCR multiplies a single, microscopic strand of genetic material billions of times within hours. This process has multiple applications in medicine, genetics, biotechnology and forensics. Because of its ability to extract DNA from fossils, PCR is also the basis of a new scientific discipline, paleobiology.